1. Field of the Invention
The present invention relates to a raw sewage disposal apparatus for disposing of raw sewage, which apparatus can be utilized in the outdoors, in a transportation means, such as a vessel or train, or in a tunnel through which a tank truck used for collecting raw sewage (hereinafter referred to as a vacuum truck) cannot go and, more particularly, to an apparatus provided with a dust collector capable of removing the dust that remains in the apparatus after drying the raw sewage and a heating means for heating catalyst means, said apparatus being capable of withstanding long use and facilitating maintenance and inspection thereof.
2. Description of the Prior Art
The raw sewage discharged from a human body is typically discharged into a sewage system by use of a flush toilet and the like, and thence into a river, after being temporarily stored in a holding tank and purified therein. However, at events, such as festivals, athletic events, fairs, meetings and the like, temporary toilet facilities must be provided to dispose of raw sewage.
Employed conventionally are movable (portable) temporary toilets, most of which have a tank for temporarily storing the raw sewage therein. However, the temporary toilets have a problem in that the raw sewage stored in the tank is sucked into a vacuum truck for collection, which is laborious and maintenance of them, after they are used, is time consuming and is nonhygienic.
Transportation vehicles, such as buses, trains, vessels, etc. which operate over long distances are provided with a tank exclusively used for storing and holding the raw sewage. The raw sewage in this tank is subjected to a deodorizing treatment by chemicals, and thereafter is collected by a vacuum truck.
As mentioned above, the raw sewage in the conventional temporary toilets or the movable transportation facilities is at first stored as it is discharged from the human body and then is collected thereafter. Accordingly, the storing method, the collection method and the disposal method all are not modern and very nonhygienic.
In an attempt to ameliorate the above problems, there have been proposed several hygienic disposal methods. In one method, for example, chemicals are introduced into the tank where the raw sewage is stored to thereby prevent the bad smell and to effect sterilization of the raw sewage. This is mainly employed in the transportation industry, such as on trains like the Shinkansen Express in Japan. This method, however, cannot be used for a long period of time because the chemicals become diluted and the costs are high.
In another method, the raw sewage is stored in a bag made of vinyl and the like to prevent diffusion of the bad smell. This method, however, requires a vinyl bag of large size and involves high cost for disposal thereof, and it is troublesome to separate the raw sewage from the bag.
In still another method, the discharged raw sewage is directly dried by use of heat from a burner, etc. Since the primary component of raw sewage is liquid, a large amount of heat energy is required to remove the liquid and it takes a long time to effect disposal of the raw sewage.
In view of the drawbacks of the conventional methods for disposing of raw sewage, the present inventor proposed a drying apparatus having a casing provided with stirring blades and heat holding bodies therein in which the raw sewage is stirred by the rotation of the stirring blades and heated by heat generated by the heat holding bodies whereby the raw sewage is dried in a short period of time. This is disclosed in Japanese Patent Laid-Open Publication Nos. 63-124150, 63-172852, 63-190857, 63-292789 and Application No. 63-198858, corresponding to U.S. patent application Ser. No. 351,029, filed May 12, 1989, now U.S. Pat. No. 4,999,930, issued Mar. 19, 1991. Another related application is U.S. Ser. No. 575,910, filed Aug. 29, 1990. According to the proposed disposal methods, the raw sewage is heated in a casing and the liquid component of the raw sewage is vaporized and diffused into the ambieht atmosphere. Before the vaporized liquid component is diffused, components which cause a bad smell are treated by the catalyst and then the vaporized liquid component is diffused into the atmosphere as an odorless vapor. It is preferable to employ such a method in view of environmental hygiene and preservation even if such method is employed around crowded buildings and occasions having throngs of people.
The elimination of the bad smell has been effected in an airtight casing. In the airtight casing, nonflammable residual substances, which are small portions of the total liquid component, remain in the casing, although most of the liquid component can be vaporized. It was necessary to remove the residual substances or dusts present in the casing. To remove such residual substances and clean the casing, the casing was disassembled so that the inside of the casing was exposed. There was a problem in that it was laborious to disassemble, clean and reassemble the casing, and the temporary toilet could not be used while the casing was undergoing disassembly, cleaning and assembly operations.
Furthermore, it was necessary that the vapor should pass through the catalyst to eliminate the odor-causing substances, such as ammonia, urea and the like, which are generated during heating of the liquid component of the raw sewage. Bad smell generating components were subjected to oxidation-reduction and were thereby rendered odorless and then they were diffused in the atmosphere. As the catalyst, precious metals, such as platinum, have been typically employed. Such a catalyst should be always kept at a constant temperature exceeding a predetermined value for subjecting the bad smell generating components to oxidation-reduction. In my companion application U.S. Ser. No. 07/784595 corresponding to Japanese-Serial Nos. 164594/90, 411577/90, 67538/91 and 189280/91, a secondary heater is disposed in a passage between an evaporation cauldron and the catalyst means and always heats the catalyst to keep the temperature of the catalyst constant. When the temperature of the vapor evaporated from the evaporation cauldron is reduced during the flow thereof and contacts the catalyst at such a lower temperature, the catalyst cannot effectively perform the oxidation-reduction. Accordingly, the vapor evaporated from the evaporation cauldron is reheated by the secondary heater, its temperature is increased and thereafter it contacts the catalyst.
If the vapor, including ammonia and urea, directly contacts the secondary heater, the secondary heater is oxidized by the components of the vapor which causes breakage and erosion of the secondary heater. These disadvantages are not desired because they increase the required maintenance of the heater. It is necessary that the secondary heater can be used for a long time.